Dinitrogen, oxygen, and nutrient fluxes at the sediment-water interface and bottom water physical mixing on the eastern Chukchi Sea shelf

We measured fluxes of net dissolved N2 and O2, NO3−, and PO4−3 at the sediment-water interface in whole cores in relation to bottom water temperature and salinity in late summer 2010 on the shelf of the eastern Chukchi Sea. Cold (−1.68 °C) and high-salinity (33.72) bottom water, characteristic of Pacific winter water, overlaid the sediment over the northeastern region of the shelf while relatively warmer (8.33 °C) and less saline (29.88) water with properties of Alaska Coastal Water covered the seabed in the southeastern region. Latitudinal variability of gas fluxes was not linked to differences in temperature or salinity. Relatively higher N2 efflux was measured for sediment located at the water mixing front between cold and warm bottom waters. Benthic O2 consumption in the southeastern region was relatively intense as were NO3− and PO4−3 effluxes from the sediments into the water column. Overall, sediments in the Chukchi Sea are sites of intense denitrification but these losses appear compensated by benthic NO3− regeneration, as NO3− efflux from sediments into the overlying water exceed those of N2. Exposure of sediment cores to incoming light did not affect benthic fluxes significantly compared to dark conditions.